1. Chemical Constituents
Harmful chemical elements such as As Sn Sb Bi Pb and NHO are needed. In order to improve the homogeneity of chemical composition and purity of steel, reduce non-metallic inclusions in billet and improve its distribution, melting furnace is often used. External refining equipment refining molten steel, and even the use of electroslag furnace remelting billet.


2. Dimensional accuracy and shape
The geometric dimensions of seamless steel pipe mainly include the diameter, wall thickness, ellipticity, length, curvature, end slope, groove angle and blunt edge of the pipe, and the cross-sectional dimensions of the relatively shaped steel pipe.


3. Surface quality
The requirement of "smooth surface" of seamless steel pipe is stipulated in the standard. Common defects are: crack, hair, bending, folding, rolling, straight inside, straight outside, separation layer, crust, pit, convex shell, pit (dent), scratch (scratch), inner spiral track, outer spiral track, blue one, crack, bending, outer folding, rolling, separation, crust, pit, convex shell and other dangers. Defects; puncture, blue line, steel pipe wear, inside and outside micro straight line, inside and outside spiral slight, correction bump and rolling printing is a general defect.


4. Physical and chemical properties
The mechanical and mechanical properties at room temperature (thermal strength and low temperature) and corrosion resistance at a certain temperature (such as oxidation resistance, water corrosion resistance, acid and alkali resistance) generally depend on the chemical composition and structure. Steel. Properties and purity of steel and heat treatment of steel. In some cases, the rolling temperature and the deformation degree of the steel tube will also affect the performance of the steel tube.


5. Technological properties, including flame, flattening, crimping, bending, ring pulling and welding properties of steel pipes.


6. Metallographic structure, including steel pipes with low and high magnification.


7. Special requirements, except those put forward by users when using steel pipes.